Hi to everyone, I'm a new to forum , so if I do or say something that I should not just please tell me!

So let's start. My question is all about a compromise between buying a Pentax K10D with 18-55mm or 16-45mm lense, but I just don't knoiw what to do... If you can explain me some detail about each of them maybe I could do my choise.

Main criteria is aperture: the lower f/, the better (more light comes into the sensor). Second main criteria is obviously price. So the DA 16-45 f4 shows a nice aperture/price solution, with a constant f/4.

I'm slightly unhappy with my 18-55mm f/3.5-5.6, so I ordered a 16-50mm f/2.8 but I can't provide you feed-back now since I'm still waiting for it! As soon as I receive it, I'll post a review as I did for the Pentax DA* 50-135 f2.8 ED (IF) SDM.

Bob provides you with the reference link I was looking for (thank you, Bob ) : http://www.photozone.de, somehow technical but very interesting.

Ah, it's nice to have some real explain.
I thank you a lot for your two message, maybe I will not buy the 16-50 now (I'm not rich for now ) but maybe the 16-45 would be an option with is constant f/4.
I will continue to make some search on it and if there is anyone who want to debate on it your invited in this post!

Here are some suggestions to ease your purchase selection. I know it's difficult

The K10D is an excellent camera (Disclaimer: I own one ) and, since it is aimed at prosumer / professional, implies a learning curve: please refer to my review and the discoveries I made.

For example, compared with other cameras, there are no special ready-to-shoot modes, as portrait, landscape and so on: such modes (actually I've never used) prevent you from being free to find the perfect adjustment.

Second, selecting both the kind of pictures you want to start with (portrait, lanscape, sport) and the available budget would greatly help to ease your selection.

Third, the K10D comes with multiple bundles with lens at very aggressive prices. For example, the body only is rated at USD 660 and the body + 18-55mm bundle has a price tag of USD 730, that is, USD 70 only for the lens!